1. Field of the Invention
This invention relates to valves for the control of mass flow and, more particularly, to a valve having separate first and second valve wings that are selectively movable between open and closed positions.
2. Background Art
There are a multitude of different valve configurations used to control mass flow, such as in the feeding of grains, cereals, packaging materials, etc. While the valve of the present invention is a general purpose valve, which has utility in many different environments, its utility in the packaging field and, more particularly, the loose fill packaging field, will be described herein only as a representative environment.
There are generally two applications for flow control valves in the loose fill industry. One such application is in converting plants in which raw resin beads are expanded in bulk and transported in high volume for processing. Due to the large volume of material being handled in such operations, the conveying conduits and flow control valves therefor are very large. Precise metering and flow control of product is unnecessary.
In a second application, the loose fill is controllably delivered into containers "on-site". These delivery systems are low volume compared to those used in converting plants. On-site loose fill packaging requires that an operator be able to precisely control the direction and quantity of discharged loose fill material.
Loose fill packaging operation- typically gravity feed discrete, expanded polystyrene particles into a container for an article to be shipped. A conduit, depending from a hopper with a bulk supply of the loose fill material has a movable discharge end for controllably directing the loose fill into the container. The operator controls a valve to arrest the feed of loose fill when a desired amount thereof is introduced into the container.
One exemplary valve is similar to that conventionally employed as a damper on a flue pipe. A flat disk is rotatable manually through a 90.degree. range between a closed position, wherein a planar surface n the disk is situated at right angles to the material flow direction and obstructs flow through the pipe, and an open position, wherein the disk planar surface is aligned generally in the flow direction to allow substantially unobstructed flow of the material.
This type of valve has several drawbacks when used in loose fill delivery systems. First, the valve, while capable of being automated, requires a fairly complicated mechanism to accomplish this end.
Another problem with this type of valve is that a significant amount of material is discharged after the valve is closed. As the valve moves from its open position to its closed position, the uppermost part of the valve plate pivots in a downward direction and in so doing sweeps additional conveying material towards the outlet.
Another type of conventional valve is a louver-type valve. This type of valve has limited applicability due to its space requirements and is therefore practical only on a large scale. If the louvers are not wide enough, the individual louvers, even in an open position, significantly obstruct material flow.
Another conventional type of control valve is a sliding gate valve. A gate is guided in translation between open and closed position in a line perpendicular to the flow direction. While this type of valve lends itself to automated operation, the gate mechanism and automating structure therefor take up a considerable amount of space. Generally, the sliding gates are movable outside of the flow space where the actuating structure therefor resides with the valve in an open position. The space demands are obvious.
A further drawback with the sliding gate valve is that the conveying material tends to interfere with the gate as it moves towards its closed position. Material may wedge between the free edge of the gate and the seat therefor as the valve moves towards its closed position.
Another type of valve conventionally used in mass flow operations is a scissors-type valve. The scissors-type valve is difficult to automate. Further, the scissors-type valve is spaced demanding, which makes it impractical in on-site packaging systems.